1. Field of the Invention
The present invention relates to a method of and an apparatus for detecting and counting articles as they are carried along or allowed to fall through a passageway across which a light beam extends and through which the articles are constrained to pass. More particularly, the present invention is directed to a method of and an apparatus for detecting articles by providing a pair of crossed light beams at a sensing plane in the passageway, to permit the detection of articles that pass through the crossed light beams, wherein the detection is independent of the orientation of the articles relative to the respective light sources, and for accurately counting the articles regardless of their shape and their orientation relative to the respective light beams.
2. Description of the Related Art
Devices for detecting and counting articles are broadly known. For example, in U.S. Pat. No. 3,618,819, which issued Nov. 9, 1971, to Charles M. Blackburn and John L. Ditman there is disclosed an electronic counting apparatus wherein the interruption of a single, thin, narrow beam of light that extends across the passageway through which articles pass is sensed by a solar cell positioned opposite the source of the light beam. The length of the output pulse from the solar cell is utilized to determine that an article has passed the sensing plane.
In U.S. Pat. No. 4,982,412, which issued Jan. 1, 1991, to Barry M. Gross, there is disclosed an apparatus and a method for counting a plurality of similar articles. That patent discloses a counter in the form of a light source and a photoelectric cell, the cell sensing interruption of the light beam. The device provides an output when the light sensor output falls below a predetermined level. The device is so configured that a predetermined time interval can be set for the duration of the detector output signal, in order to avoid overcounting.
In U.S. Pat. No. 4,675,520, which issued Jun. 23, 1987, to Jan Harrsen et al., there is disclosed a counter for counting small particles, such as seeds, by providing crossing light beams that are operated in synchronization in sequential scanning cycles to provide pulses in two perpendicular directions, the pulses being multiplied together to provide a unitary output signal indicative of the presence of a particle to be counted.
Although the prior art has disclosed the provision of arrangements for detecting and counting articles that pass through a light beam defining a sensing plane, and thereby interrupt the beams of light as a result of the passage of the articles, most of the prior art devices are directed to sensing symmetrical objects that provide similar detector outputs in each of two different directions.
It is an object of the present invention to overcome the deficiencies of the prior art devices and to provide an article detecting and counting method and apparatus for accurately counting non-symmetrical articles.
It is another object of the present invention to provide an article detecting and counting apparatus that is relatively simple and inexpensive to manufacture and to maintain, and that is both accurate and reliable.